Telephone-exchange system.



No. 655,810. Patented Aug. 14, I900! A. STROMBEBG & w. m. DAVIS. TELEPHONE EXCHANGE SYSTEM.

(Application filed Apr. 26, 1899.)

(No Model.) 7

Q Q m m: Noam; PETERS co. mmou'mu. WASHINGTON. 0. c

STATES PATENT Fries.

ALFRED STROMBERG AND WILLIAM M. DAVIS, or cnIcAeo, iL InoIs, ASSIGNORS TO THE STROMBERG-OARLSON TELEPHONE MANUFAC- TUBING COMPANY, OF SAME PLACE.

TELEPHONE-EXCHANGE SYSTEM.

SPECIFICATION forming part of Letters Patent No. 655,810, dated August 14, 1900.

Application filed April 26, 1899. Serial No. 714,536. (No model.)

To all whom it may concern:

Be it known that we, ALFRED STROMBERG and WILLIAM M. DAVIS, citizens of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented a certain new and useful Improvement in Telephone-Exchange Systems, (Cases Nos. 2 and 1,) of which the following is a full, clear, concise, and exact description, reference being bad to the accompanying drawings, forming a part of this specification.

O in invention relates to telephone-exchange systems, and more particularly to that class of telephone systems in which centralized batteries are employed fbr supplying the transmitter-circuits at the subscribersstations with current. Our invention has for one of its objects the provision of improved circuits and apparatus whereby special clearing-out indicators may be dispensed with, one of the line-indicators being retained in connection with an established circuit between subscribers, and thereby performing the function of a clearing-out indicator.

Our invention in its preferred embodiment relates more particularly to multiple-switchboard telephone-exchange systems, and by its use we are enabled to prevent the false operation of the caHedsubscribers line-indicator, that may be located at another section of the switchboard, the line-indicator of the calling subscriber being preferably the one that acts as a clearing-out indicator upon the establishment of a connection between subscribers.

The invention also has for its object the provision of means whereby the coil or winding of the line-indicator that is used as the clearing-out indicator may be used as an impedance-winding to pre ven t the passage ofvoicecurrents and at the same time to permit of the flow of battery-current over the line. In order to maintain a balance of the system, we also preferably employ a second impedancewinding, which acts in the same capacity. Each telephone-line is thus provided with an annunciator or indicator having a winding which acts as an exciting-winding and also as an impedance-windingand in addition to this winding a second Winding which acts solely in the capacity of an impedance-winding. For the sake of convenience the two windings thus associated with each'line are wound upon a common core, provision being made, however, to prevent that winding which acts solely as an impedance-winding from influencing the armature of the indicator. The centralized battery is preferably not included directly in the cord-circuit, as this would necessitate in the best telephone practice the employment of repeating-coils. The limbs of the telephone-lines are extended beyond their line-switches or spring-jacks to the common battery, from which the operators telephone outfit is also supplied.

The invention has for its further object the provision of improved means whereby the testthimbles of connected lines may be charged.

We will explain ourinvention more particularly by reference to the accompanying drawings, in which v Figure 1 illustrates the preferred embodiment of our invention as applied to a multiple-switchboard telephone-exchange system. Fig. 2 illustrates, diagrammatically, the circuits that are established upon the connection of subscribers for conversation.

Like characters of reference refer. to like parts in both views.

The apparatus at the substations 10 and 90 is well known to those skilled in the art. A transmitter a, with its coil b, and the receiver 0, with its coil, are shown at each station, the secondary coil in circuit with the receiver beingincluded in a local circuit therewith, while the primary coil in circuit withthe transmitter is placed in series with both limbs of the corresponding telephone line upon the removal of the receiver from its spring switchhook. The transmitter primary winding of the induction-coil is thus shown in series with the telephone-line, the telephon e-receiver bein g removed from its book. The transmittercircuit at station 90 is open, the receiver at said station'being upon its hook. There is each bell being preferably placed with the condenser in a bridge between the limbs of each telephone-line, the telephone-lines extended from the substations to the exchange being connected with the sections 3, 2, and 1 of the multiple board. We prefer to employ at the answering-sections of the switchboard a special answering-jack in addition to the regular line-jack, the jacks g at board 1 being the regular line-jacks, while the jacks 7t at board 1 are the answering-jacks. The linejacks are preferably each equipped with two long and one short line-spring, the longer springs being adapted for engagement with the sleeves of a connecting-plug, while the shorter spring is adapted for connection with the tips of the connecting-plugs. The answering-jacks, however, are preferably each equipped with but two springs, the shorter spring being adapted for engagement with the tips of the connecting-plugs, while the longer spring is adapted for engagement with the sleeves of the connecting-plugs. The two longer line-springs of each line-jack and the longer line-spring of each answeringjack are adapted to be electrically connected with the test-thimbles (indicated in section in front of the line-springs) by the sleeve of any inserted plug. The upper line-spring and the shortest line-spring of each line-jack are adapted by their engagement respectively with the sleeve and tip of the connecting-plug engaging the same to effect a continuation of the telephon eline connected with said springs through the operatorscord-circuit. Thelower line-spring of each line-jack is provided with a back contact normally engaging the same, by means of which and the connections shown one of the limbs of each of the telephone-lines is normally extended to one pole of the common battery 2'. Theexciting-winding 7t of each line-indicator is normally included in series with the longest line-springs of the line-jacks and the back contacts engaging the same, and consequently also with the limb of the telephone-line normally connected with the longers n, whereby when said impedance-winding thereby closing the circuit from the battery '11 through the actuating-coil 7c of his line-indicator and the limbs of the telephone-line.

The operator in response to the signal conveyed-by the indicator 7c inserts the answering-plug of one of her cord sets into the answering-jack of the calling subscriber. It will be observed that the circuit connections of the answering-jacks are such that upon the insertion of the answering-plug the coil 76 of the calling-subscribers indicator is not cut out of circuit, whereby this indicator is adapted to serve the purpose of a clearing-out indicator, the indicating magnet being constantly excited during the time that the call-- ing subscriber keeps his telephone-receiver from its hook. This same coil or winding 70 of the calling-subscribers line-indicator we also employ as an impedance-winding, the extra coil or winding upon the core of the calling-subscribers indicator being excluded from circuit by the depression of the longer line-spring of the answering-jack from its back contact, which forms one terminal of the latter coil.

The operator manipulates her keyp to throw her telephone into circuit with the callingsubscribers telephone and, ascertaining that the said subscriber. desires communication with the called subscriber 90, inserts the connecting-plug q into the line-jack g of the called-subscribefs line. By this act, as will be apparent by an inspection of the drawings, the circuit through the coil 70 of the calledsnbscribers line-indicator is opened at the back contact normally engaging the longest line-spring of the said'line-jack, the extra impedance-coil Z upon the core of the called-subscribers line-indicator being maintained in circuit, no plug being inserted within the answering-jack h of the called subscriber, the answering-jacks controlling the continuity of thecircuitoftheextraimpedance-coilsl. The operator manipulates the key 19 to operate the signal-bell at the called-subscribers station.

Upon the establishment of the telephonecircuit between two subscribers according to our invention We include the centralized battery i in a bridge between the sides of the combined circuit uniting the subscribers for telephonic communication, two impedancecoils being included in the same bridge, one

upon each side of the battery, wherebya balance is maintained between the sides of the system, one of these impedance-coils being a coil of a line annunciator or indicator and the other impedance-coil being one thatacts solely as such. The coil is of the called-subscribers line-indicator being thus opened upon the establishment of the connection with his line, the said indicator is not operated upon the actuation of the called-subscribers teleph0nehook. When the subscribers are through conversation, their receivers are restored, the clearing-out signal being given by the line-indicator of the calling subscriber in being restored to its normal condition. Upon this signal the plugs uniting the subscribers lines are Withdrawn from their engaging springjacks.

In a multiple-switchboard system, where the called subscriber may have his annunciator located at another section of the switchboard than that where the calling-subscribers annunciator is located, it is possible by means of our invention to render the said calledsubscribers annuneiator inoperative during an established connection, whereby false signals to the operator at the calledsubscribers section of the switchboard are prevented. Preferably in accordance with our invention when employed in connection with multiple switchboards the association of the impedance-coils with the united telephonelines is the same irrespective of the location of the annunciators of the connected subscribers. This association of the coils with the united telephone-lines is shown more clearly in Fig. 2, in which the exciting-coil of the calling-subscribers line-indicator is included between one terminal of the common battery and a side of the telephone-circuit between the subscribers, the extra impedancecoil Z, associated with the called-subscribers line, being included in circuit between the other terminal of the battery and the remaining side of the telephone-circuit. The extra impedance-coil associated with the callingsubscribers telephone-line is cut out of circuit, as is also the exciting-coil of the calledsubscribers indicator.

The test-thimbles of the calling-subscribers spring-jacks upon the different sections of the switchboard are connected with the centralized battery by means of the sleeve of the inserted answering-plug and the long linespring of the answering-jack engaging said sleeve. The test thimbles of the called-subscribers spring-jacks upon the different sections of the switchboard are charged with current from the battery i by way of the tip of the answering-plug, which is connected with the sleeve of the connecting-plug, the latter sleeve engaging a test-thimble of one of the called-subscribers spring-jacks. The sleeve of the answering-plug and the tip of the connecting-plug are connected. The test-thimbles of the calling-subscribers spring-jacks are also charged with battery-current by way of the tip of the connecting-plug and the cordstrand uniting said tip with the sleeve of the answering-plug.v By connecting the tips with the sleeves and the sleeves with the tips of the plugs we are enabled to transfer batterycurrent for the purposes of testing from one section of a switchboard to another through the agency of the cord-strands and without the necessity of employing special cord-strands which do not take part in the propagation of the voice-currents.

The operators outfit is preferably associated with the cord-circuit, as shown, whereby the operator may receive calls and readily listen in at any time and whereby she also may test the electrical condition of a called line. The operators transmitter is preferably supplied from the same common battery,

and impedance-coils r r of sufficiently-high -While we have shown one particular type of switchboard and one peculiar arrangement of the operators cord-circuit and a special construction for the line and answering spring-jacks, we do not wish to be limited to V the precise embodiment of these features shown nor to the precise circuits shown but,

Having described our invention, we claim as new and desire to secure by Letters Patcut- 1. In a telephone-exchange system,the combination with two telephonedines extending from substations to an exchange, of telephone switch-hooks at each of the substations for opening and closing the'telephone-line at each substation; a centralized battery normally included in circuit with the said telephonelines; a line-indicator for each of said telephone-lines, each normally included in circuit with said battery, whereby upon the completion of the circuit at either of said subscribers stations the indicator corresponding to said station is operated, which station thus becomes the calling station; a cord-circuit for forming a continuation of one of said telephone-lines means for eiiecting a connection between said cord-circuit and telephone-line without disconnectingthe line-indicator corresponding to the said line from circuit; a jackswitch, and a connecting-plug united with said cord-circuit for effecting the connection of the cord-circuit and its connected telephone-line with the remaining telephone-line, said jack-switch being adapted upon the insertion of the said connecting-plug to disconnect the indicator from the said telephone line, substantially as described.

2. In a multiple-switchboard telephone-exchange -system,the combination with two telephone-lines, each extending to a plurality of sections of a multiple switchboard and connected at each of said sections with a jackswitch, of telephone switch-hooks at each of the substations for opening and closing the telephone-line at each substation; a centralized battery normally included in circuit with the said telephone-lines; a line-indicator for each of said telephonelines, each normally included in circuit with said battery, whereby, upon the completion of the circuit at either of said subscribers stations, the indicator' corresponding to said station is operated, which station thus becomes the calling station; a cord-circuit for forming a continuationof the telephone-line extending from the calling station; means foreffecting a connection between said cord-circuit and said calling telephone-line without disconnecting the line-indicator corresponding to the said line from circuit, and a connecting-plug united with said cord-circuit adapted for insertion within a jack-switch of the remaining or called-subscribefis telephone-line to effect the connection of the cord-circuit with the remaining or called telephone-line, said jackswitch being adapted upon the insertion of the said connecting-plug to disconnect the indicator from the said telephone-line, substantially as described.

3. Inatelephone-exchangesystem,thecombination with two telephone-lines extending from substations to an exchange, of means at each of the substations for opening and closing the telephone-line at each substation; a centralized battery normally included in circuit with the said telephone-lines; a line-indicator for each of said telephone-lines, each normally included in circuit with said battery, whereby upon the completion of the circuit at either of said subscribers stations the indicator corresponding to said station is operated, which station thus becomes the calling station; a cord-circuit for forming a continuation of one of said telephone lines;

means for eifectin g a connection bet ween said cord-circuit and telephone-line without disconnecting the line-indicator corresponding to thesaid line from circuit; a jacloswitch, and a connecting-plug united with said cordcircuit for efiecting the connection of the cord-circuit and its connected telephone-line with the remaining telephone-line, said jackswitch being adapted upon the insertion of the said connecting-plug to disconnect the indicator fromthe said telephone-line, substantially as described.

4. Ina multiple-switchboard telephone-exchange system, the combination with two telephone-lines, each extending to a plurality of sections of a multiple switchboard and connected at each of said sections with a jackswitch, of means at each of the substations for opening and closing the telephone-line at each substation; a centralized battery normally included in circuit with the said telephone-lines; a line-indicator for each of said telephone-lines, each normally included in circuit with said battery, whereby, upon the completion of the circuit at either of said subscribers stations, the indicator corresponding to said station is operated, which station thus becomes the calling station; a cord-circuit for forming a continuation of the telephone-line extending from the calling station means for effecting a connection between said cord-circuit and said calling telephone-line without disconnecting the line-indicator corresponding to the said line from circuit, and a connecting-plug united with said cord-circuit adapted forinsertion within a jack-switch of the remaining or called-subscribers telephone'line to effect the connection of the cord-circuit with the remaining or called telephone-line, said jack-switch being adapted upon the insertion of the said conmeeting-plug to disconnect the indicator from the said telephone-line, substantially as described.

5. In a multiple-switchboard telephone-ex change system,the combination with two telephone-lines, each extending to a plurality of sections of a multiple switchboard and connected at each of said sections with a linejack switch, of telephone switch-hooks at each of the substations for opening and closing the telephone-line at each substation; a centralized battery normallyincluded in circuit with the said telephone-lines; a line-indicator for each of said telephone-lines, each being located at one section of the switchboard and normally included in circuit with said battery, whereby upon the completion of the circuit at either of said subscribers stations the indicator corresponding to said station is operated, which station thus becomes the calling station; an answering-jack for each telephone line'located at the same section of the switchboard with each line-indicator of said line; a cord-circuit for forming a continuation of the telephone-line extending from the calling station; an answering-plug connected with said cord-circuit for insertion within the answering-jack of the calling line, said answering-jack and answering-plug beingadapted to effect connection between the calling line and the cord-circuit without disconnecting the line-indicator of said line from circuit, and a connecting-plug adapted for insertion within a line-jack of the remaining or ealled-subscribers telephone line, said line-jack being adapted to effect the exclusion of the called-subscribers lineindicator from circuit with the battery upon the insertion of the connecting-plug to prevent the operation of said line-indicator during the connection bet-ween the telephonelines, substantially as described.

6. In a multiple-switchboard telephone-exchange system, the combination with two telephone-lines, each extending to a plurality of sections of a multiple switchboard and connected at each of said sections with a linejack, of means at each of the substations for opening and closing the telephone-line at each substation; a centralized battery normally included in circuit with the said telephone-lines; a line-indicator for each of said telephone-lines, each being located at one section of the switchboard and normally included in circuit with said battery, whereby upon the completion of the circuit at either of said subscribers stations the indicator corresponding to said station is operated, which station thus becomes the calling station; an answering-jack for each telephone-line located at the same section of the switchboard with each line-indicator of said line; a cordcircuit for forming a continuation of the telephone-line extending from the calling station; an answering-plug connected with said cord-circuit for insertion within the answering-jack of the calling line, said answeringjack and answering-plug being adapted to effect connection between the calling line and the cord-circuit without disconnecting subscribers telephone-line, said line-jack being adapted to eitect the exclusion of the called subscribers line-indicator from circuit with the battery upon the insertion of the connectingplug to prevent the operation of said line-indicator during the connection between the telephone-lines, substantially as described.

7. In a telephone exchange system, the combination with two telephone-lines extendin g from substations to an exchange, of a centralized battery normally in circuit with said telephone-lines; a transmitter-circuit at each subscribers station adapted to be supplied with current from said centralized battery over the telephone-line; a telephone switchhook at each station for controlling the continuity of the transmitter-circuit thereat; one impedance winding, constituting also the winding of a line-indicator, and an extra impedance-winding provided in connection with each telephone-line, each indicator-winding being normally included in circuit with the battery and adapted to be excited upon the removal of the receiver from its switch-hook; means for establishing telephonic circuitbetween the substations for conveying voicecurrents, and additional means cooperating with said means adapted upon the completion of circuit between subscribers stations to include the winding of a line-indicator of one of said lines in bridge between the battery and one side of the telephone-circuit uniting the subscribers stations and the extra impedance-Winding of the other telephoneline in the same bridge between said battery and the other side of the telephone-circuit and serving to exclude the remaining impedance and line-indicator windings from circuit, substantially as described.

8. In a telephone exchange system, the combination with two telephone-lines extending from substations to an exchange, of a centralized battery normally in circuit with said telephone-lines a transmitter-circuit at each subscribers' station adapted to be supplied with current from said centralized battery over the telephone-line; a telephone switchhook at each station for controlling the continuity of a transmitter-circuit thereat; an impedance Winding constituting also the winding of a line-indicator associated with each of said lines and normally in circuit with said battery and telephone-line and adapted to be excited upon the removal of the teleph0ne-receiver from its switch-hook; a cordcircuit for forming a continuation of one of said lines; a plug connected with the cordcircuit for connecting the remaining telephone-line with said cord-circuit, and means controlled by the apparatus for uniting the subscribers for conversation for excluding one of the line-indicator windings from circuit with said battery and including the other line-indicator winding and the said battery in a bridge between the sides of the telephone circuitbctween the substations, substantially as described.

9. In a multiple-switchboard telephone-exchange system,the combination with two telephone-lines, each extending to a plurality of sections of a multiple switchboard and 0011- nected at'each of said sections with a linejack switch, of telephone switch-hooks at each of the substations for opening and closing the telephone-line at each substation; a central ized battery normally included in circuit with the said telephone-lines; one impedance-winding, constituting also the winding ot a lineindicator, and an extra impedance-winding provided in connection with each telephoneline, each indicator-winding being normally included in circuit with the battery and adapted to be excited upon-the removal of the receiver from its switch-hook; means for establishing telephonic circuit between the substations forconveyiug voice-currents, and additional means cooperating with said means adapted upon the completion of circuit between subscribers stations to include the winding of the line-indicator of one of said lines in bridge between the battery and one side of the telephone-circuit uniting the subscribers stations and the extra impedancewinding of the other telephone-line in the same bridge between said battery and the other side of the telephone-circuit and serving to exclude the remaining impedance and line-indicator windings from circuit, substantially as described.

10. In a inultiple switchboard telephone-exchange system, the combination with two telephone-lines, each extending to a plurality of sections of a multiple switchboard and connected at each of said sections with a line-jack switch, of telephone switch-hooks at each of the substations for opening and closing the telephone-line at each substation; a centralized battery normally included in circuit with the said telephone-lines; a line-indicator as sociated with each line, the winding of each indicator being also an impedancewinding, the winding of each indicator being normally in circuit with said centralized battery and being excited upon the removal of the receiver from the corresponding telephone switch-hook, the line corresponding to the indicator thus excited becoming the calling line; an additional impedance-winding associated with each line; an answering-jack connected with each line and located atthe same section of the switchboard with the line-indi cater; an answering-plug adapted for insertion within said answering-jack and being adapted thereby to effect the connection of the calling line with the cord-circuit without interrupting the circuit through the indicat ing-winding, said plug and answering-jack being adapted to effect the disconnection of the additional impedance-Winding associated with said calling line, and a connecting-plug adapted for insertion within line-jack of the remaining or call.ed-subscribei"s telephoneline, said plug and line-jack being adapted to exclude theindicator-winding of the called subscriber Without excluding the additional impedance-winding associated with the called line, said plugs, by means of suitable circuit connections, being adapted to include the battery between the connected impedance- Winding and indicator-winding in a bridge 1 including said windings across the telephonepaths for testing current from the tips to the sleeves; a test-battery, and switch parts at the jack-switches connected with said testbattery and adapted for engagement with the tips of said plugs upon the insertion thereof within the jack-switches, whereby said testthimbles are charged with current from said test-battery through the agency of the cordstrands independently of the subscribers apparatus, substantially as described.

12. In a n1ultiple-switchboard system, the combination with two telephone-lines, each extending toaplurality of sections of a multiple switchboard and connected at each of said sections with a jack-switch, of test-thimbles, one associated with each of said jackswitches, the test thimbles of the jackswitches associated with each line being electrically connected, a testing-circuit for the test-thimbles independent of the subscribers apparatus, connecting-plugs having a tip and sleeve connected bya cord-strand, a test-battery adapted for connection with a set of said thimbles and said strand, and a switching portion at each jack connected with said testbattery and adapted for engagement with the said tip upon its insertion within a jackswitch, thereby to connect the test-thimble engaging the said sleeve with the test-battery, through the agency of the said cordstrand, substantially as described.

13. In a telephone-exchange system, the combination with two telephone-lines extending from substations to an exchange, of a centralized battery normally in circuit with said telephone-lines, a transmitter-circuit at each subscribers station adapted to be supplied with current from said centralized battery over the telephone-line, a telephone switchhook at each station for controlling the continuity of the transmitter-circuit thereat, an impedance -winding constituting also the winding of a line-indicator associated with each of said lines and normally in circuit with said battery and telephone-line and adapted to be excited upon the removal of the telephone-receiver from its switch-hook, a cordcircuit for forming a continuation of one of said lines, a plug connected with the cordcircuit for connecting the remaining telephone-line with said cord-circuit, an addi tional impedance-winding, and means controlled by the apparatus for uniting the subscribers for conversation for excluding one of the line-indicator windings from circuit with said battery and including the other line-indicator Winding and the additional impedance-winding in a bridge with said battery betweenthe sides of the telephone-circuit between the substations, substantially as described.

14. In a telephone-exchange system, the combination with two telephone-lines extendin g from substations to an exchange, of a centralized battery normally in circuit with said telephone-lines, a transmitter-circuit at each subscribers station adapted to be supplied with current from said centralized battery over the telephone-line, a telephone switchhook at each station for controlling the continuity of the transmitter-circuit thereat, an impedance -winding constituting also the winding of a line-indicator associated with each of said lines and normally in circuit with said battery and telephone-line and adapted to be excited upon the removal of the telephone-receiver from its switch-hook, a cordcircuit for forming a continuation of one of said lines, a plug connected with the cordcircuit for connecting the remaining telephone-line with said cord-circuit, an additional impedance-Winding, and means controlled by the apparatus for uniting the subscribers for conversation for excluding one of the line-indicator windings from circuit with said battery and including the said battery between the other line-indicator winding and the additionalim pedance-windingin a bridge between the sides of the telephone-circuit, substantially as described.

15. In a telephone-exchange system, the combination with two telephone-lines extending from substations to an exchange, of a centralized battery normallyin circuit with said telephone-lines, a transmitter-circuit at each subscribers station adapted to be supplied with current from said centralized battery over the telephone-line, a telephone switch hook at each station for controlling the con tinuity of the transmitter-circuit thereat, an impedance winding constituting also the winding of an indicator, a cord-circuit for forming a continuation of one of said lines, a plug'connected with the cord-circuit for connecting the remaining telephone-line with said cord-circuit, two additional impedance Windings,one associated with each telephone line, and means controlled by the apparatus for uniting the subscribers for conversation cord-circuit for forminga continuation of one of said lines, a plug connected With the cordcircuit for connecting the remaining telephone-line with said cord-circuit, and means controlled by the apparatus for uniting the subscribers for conversation for including an impedance-Winding, the battery and said indicator-winding in the circuit between the substations, substantially as described.

In Witness whereof We hereunto subscribe our names this 24th day of April, A. D. 1899.

ALFRED STROMBERG. WILLIAM M. DAVIS. Witnesses:

GEORGE L. CRAGG, CHARLES E. HUBERT. 

